With $1 billion in sales in 3 days, GTA V is a huge hit.
For comparison, here is a link to the numbers for the first 10 weeks of unit sales of Black OPS II.  http://www.vgchartz.com/game/70716/call-of-duty-black-ops-ii/Global/
I think the ratios here can tell us a lot about what to expect for GTA V. During weeks 2 through week 10, Block OPS II did 79% of its week one amount. 
We know GTA V did 16.5 million units in the first three days and will maybe do 20 million units in week one.  That is 1.20 billion in retail sales.  Based on GTA IV revenue arrangements, 50% of the retail sales amount makes it back to TTWO.  So, I estimate almost $600 million to hit TTWO in week one.  In the June Quarter, equity(book value) was $606 million. Total market cap today is $1.672 billion.
If TTWO mirrors Black OPS II, 79% of the week one amount may get added over the next nine weeks or another $474 million.  Trim our estimate a tad and you get $1.05 billion added to equity or just over 1.6 billion of equity(book value) by mid November. That doesn't yet get us into Christmas where we can see from the link above that Black Ops II had a bump up in weekly revenue.  This also does not include "downloadable content", nor does it provide an allowance for increased interest in New Xbox and New Playstation 4 consoles coming on the market in November  http://www.dailymail.co.uk/sciencetech/article-2411912/XBox-One-Playstation-4-November-release-dates-mean-Christmas-console-war.html
I don't think it would be unreasonable to project 1.8 billion of equity (book value) by December 31 and a price to book of 1.4 would get us to $2.52 billion or 27.12 price per share.  Excitement could easily take us to 1.6 times bookvalue.
All this heavy trade in TTWO at the rising 50 day moving average seems to agree as it appears to be net buying as of today.  Fidelity and Vanguard funds are six of the top seven funds that own TTWO.
I find myself remembering Loeb's caution, "Instead of rushing in on some important, well planned and carefully checked, and seemingly conclusive single line of thought, form a composite opinion".  So I will maintain my stops and hold back some cash.